Leg presses can give added support to the lower back because of the brace effect of the seat your sitting on. With squats, not so much. Though front squats may offer less lower back stress than regular squats. As any exercise, where the bar is resting directly on the shoulders/neck/traps , the spine (in direct line) will be affected. Some find less lower back stress, when doing leg presses, by doing one leg at a time. Not too sure what you mean by "mat' when doing leg presses. You laying on a floor mat; under a old style machine, bar placed on your feet, etc...? Coming down 90 degrees is not the best of ideas. Not too many people do. Try breaking a bit before that.

Many times a lower back will need a proper warmup. Most lower backs lack hardly any range of flexibility, being stiff with limited motion. This can cause serious injury, sooner or later. Something to consider with a bad, or potentially bad, lower back. Keeping the lower back warm doing exercise is a good idea.

Didn't say if you ever used a Hack machine or have done BB Hacks. Less stress seems to be gained with the weight (BB) held below the waist/near the center of the body. Only exception would be the DL, where leaning forward, into the weight, can also put unneeded focus on the lower back.

Might get the back checked, just to clear the mind, one way or another, if you do have a ruptured disc. Good Luck.

OK, if one legged presses seem not to bother the back, than the problem might be that your back is out of spinal alinement. This might eliminate the disc theory, though an X-ray wouldn't hurt. In any event, this may suggest a visit to a chiropractor. Some back alinements have also been helped by acupuncture and deep sports/Rolfing messages.

Another notion is that the one legged press , your doing, may actually correct or help with the misplaced spine/back/hip area. A basic problem may be spinal/hip/glut flexibility as a core problem. Flexibility is much overlooked by most trainee's. Once the back problem is relieved, you may wish to go back to regular squatting.

JPM: interesting. Is it possible that a simple visit to the chiro could correct my lower spine and get rid of the issues?

You mention flexibility, etc. I notice that getting off the couch and off the flat bench after doing flat dumbbell presses is very difficult without lower back pain. Flexing my abs to get off the bench/couch actually hurts my back in these motions. (getting off the bench and couch, etc.)

What I've learnt now with squats is to not go all the way to the bottom as it causes the lower back to arch.I now use a power-lifting wider stance and go to parallel or slightly lower if using lighter weights. I've found this to be much easier on the back and have no problems now.

What I've learnt now with squats is to not go all the way to the bottom as it causes the lower back to arch.I now use a power-lifting wider stance and go to parallel or slightly lower if using lighter weights. I've found this to be much easier on the back and have no problems now.

I've noticed that going wider is easier on my knees. I think it incorporates more quad too.. but that just may be me.

Leg presses make my knee caps sting. Funny pain.. It's gotta be from years of lifting.

And again, last night I hit leg press using a single-leg approach. My lower back this morning feels less painful than even on a morning that I DIDN'T hit legs the night prior~!

Something about single legged presses seems to be loosening something up, or perhaps aligning something for me in the lower back region. Maybe the pain in the lower back isn't herniated disc pain like I originally thought, but perhaps is just that my spine is misaligned down there.

I think i'll book a trip to the chiropractor's office to see if he can crack it.

If you do have it checked out you may even discover that one leg might be shorter than the other. Most chiropractors will check this first, which is not all that uncommon in people. Also the tilt of the hips/pelvic area. Or you just might want to continue with the one leg at a time leg press experiment and see where that may lead you. Adding ham/lower back stretches may be a good idea to think about, one leg at a time.

Serious athletes will, at times, work one side of the body and than the other, insuring that no side dominates (or is weaker) the other as far as strength, speed, timing is concerned. Which all may be a good ideas for some less experienced BB'ers to try, to keep an equal (almost..one side will be a bit larger/stronger, or slightly different shape, than the other side, not matter what) muscle size balance on both sides of the body. Good Luck.